1. Field of the Invention
The present invention relates to an ion beam treating apparatus and more particularly, to an ion beam treating apparatus such as an ion beam milling apparatus, an ion beam sputtering apparatus, or an ion implanting apparatus, that is adapted to irradiating a work piece which is to be treated with an ion beam while rotating and revolving the work piece.
2. Description of the Prior Art
In a conventional ion beam treating apparatus such as an ion beam milling apparatus, in general, the irradiation surfaces of wafers on a rotary disc are tilted relative to the irradiating direction of the ion beam and are irradiated with the ion beam while rotating and revolving the rotary disc. In order to prevent adhesion of matter by sputtering or to remove adhesion of matter by sputtering, the wafers must be irradiated with the ion beam obliquely.
In the ion beam milling apparatus, the acceleration voltage with the ion beam is as low as several hundreds of volts to several thousands of volts and, hence, the ion beam is emitted over from the ion source with wide angle of divergence. Since the rotary disc which consists of a linear flat type disc is provided in a tilted manner, the respective irradiation surfaces of wafers on the rotary disc maintain different distances with respect to the ion source.
The above-mentioned type of the ion beam milling apparatus has been disclosed in, for example, a journal "IONICS, Hardware in the Ion Beam Etching Technology", August, 1981.
According to the conventional ion beam milling apparatus, a rotary disc is disposed in a tilted manner in a vacuum vessel, and a shaft is formed together with the rotary disc as an unitary structure to transmit the rotational force thereto. On the rotary disc are arranged a plurality of wafer holding portions to hold the wafers that are to be treated. The wafers on the wafer holding portions are irradiated with the ion beam emitted from an ion source while rotating the shaft and the rotary disc.
With the conventional ion beam milling apparatus of the type in which the rotary disc is rotated and revolved in a tilted manner, however, the respective wafers on the wafer holding portions of the rotary disc are irradiated with the ion beam maintaining distances relative to the ion source, the distances being different by an angle of tilt of the rotary disc. Namely, the respective wafers on the wafer holding portions are not uniformly treated by the ion beam because the different distances between the ion source and the respective wafers to be treated. The each of the wafers do not be irradiated with the ion beam maintaining the uniform intensity.
Furthermore, when an ion source with a large diameter is used so that an increased number of wafers can be treated at one time, differences of the respective wafers further increase in the distances relative to the ion source. Therefore, it becomes more difficult to uniformly treat the respective wafers, presenting serious bottleneck for finely patterning the thin films for semiconductors.